1. Field of the Invention
The present invention relates to equipment, in particular pressurized gelling equipment, to fill one or more casting molds with castable liquid materials. The castable materials are individually fed by pumps through conduits with shutoff devices to at least one plunger-cylinder system, then individually moved into a mixing chamber and from there to the particular casting mold.
2. Description of Related Art
German patent 34 20 222 describes equipment for metering castable components containing fillers comprising a pumping cylinder receiving a sliding plunger. The plunger divides the cylinder on one hand into a pump chamber with an intake and an outlet valve, communicating with a storage vessel receiving the component, and on the other hand into an operating chamber connected with a container receiving the drive liquid driving the plunger. A clearance-seal is provided between the two cylinder spaces. The drive liquid is selected in such manner as to be compatible with the individual component. The operative plunger surfaces come in contact with the drive liquid, and the individual components are substantially the same size; thus, substantially the same pressure is present on both sides of the plunger.
This equipment also provides that components containing fillers can be processed without deleterious leakages degrading equipment operation, even from storage vessels under vacuum. Sealing the plunger by a clearance-seal assures that the pumping cylinder shall be insensitive to abrasive fillers in the casting resin. This document further discloses using at least two plungers each filled with the individual component, said plungers being driven by a rigid mechanical coupling in the form of a plunger yoke. In an alternative embodiment, this document describes a stepped cylinder wherein again two cylinder chambers are formed for the components. Such known systems are preferentially used to seal the buffer(s), in particular with respect to abrasive fillers.
In DE 34 20 222 it is not disclosed that the plunger-cylinder system is designed for a high operational pressure, but instead discloses an air pressure in the range of 6-15 bar. Because of flammable material being used, the use of air pressure of 100 bars is not acceptable.
German patent document 42 08 769 A1 discloses equipment for filling one or more casting molds with castable materials, the individual components being held in storage vessels each of which is fitted with one pump. To process rapid-setting casting materials of which the individual components are prepared at precisely specified mixing ratios, this document provides that the pumps be connected to at least one synchronizing metering system through conduits that can be shut off by valves, and in that the metering system consist of at least two metering chambers within which mechanically yoked metering plungers are made to move in controlled manner. The synchronizing metering system is connected by conduits which can be blocked by valves and through an in-line mixer with at least one casting spout. This equipment allows accurate observation of the mixing ratios. The individual components can be accurately metered and continuously intermixed in the mixer. German patent document 42 08 769 A1 furthermore provides with respect to rapid-setting casting materials that the volume of casting material be minimized in the mixing and feed zones. However this known equipment is used foremost to shift the material preparation to the casting mold in order to minimize the reacting material in the supply conduits and elements. Thus German patent document 42 08 769 A1 discloses a system wherein the pumping arrangement is provided upstream of the metering arrangement.
As regards high-viscosity casting resin and short pot life, there is a requirement for small mixing chambers to preclude the material from hardening in the feed conduits. On the other hand such small mixing chambers entail high flow impedance in turn requiring commensurate pumping power to achieve the predetermined flow.
On the other hand an increase in pumping power--especially where the casting materials are abrasive--entails high wear in the pump zone. Moreover high pumping power demands lower metering accuracy by the pump.
In the light of this state of the art, it is the object of the invention to further develop equipment of the initially cited kind in such manner that especially abrasive casting materials of higher viscosity and short pot life can be processed.
The invention solves this problem in that at least one plunger-cylinder system shall be designed for a substantially higher operating pressure than that in the pumps and in that the mixing-chamber volume is relative small.
In the equipment of the invention, at least one plunger-cylinder system assume(s) the function of a pressure converter. The output pressure generated by the buffering element, respectively, is substantially higher than the pressure of the pumps associated with the storage vessels. This output pressure is controlled in such manner that it suffices also for abrasive casting materials of high viscosity and short pot lives precisely in association with the small mixing chamber provided by the invention. Illustratively at least one plunger-cylinder system can be designed for an operational pressure in the range of 10 to 200 bars and more; at an operational pressure of 100 bars and an assumed plunger diameter of 250 mm, the plunger will exert a compression of 4.9.times.10.sup.4 kp. The pumps associated with the storage vessels do not undergo the mold-filling procedure proper and compared with the plunger-cylinder systems may be designed for considerably lower output pressures, as a consequence of which wear due to high pumping power is not experienced. Another advantage of the invention is that the pumps associated with the storage vessels no longer are required to function as metering means because this function is now assumed by at least one system of plunger and cylinder. Consequently the pumps are simpler in design and operation and thereby more economical.
In the invention the single system of plunger and cylinder with two cylinder chambers for the individual components may be used, where called for with a clearance-seal such as disclosed in the German patent 34 20 222 or with other sealing means between the plunger(s) and the cylinder wall. Again at least two plunger-cylinder systems may be provided for the individual casting components, communicating with one common or several mixing chambers.
Illustratively at least one plunger-cylinder system can be powered by a drive liquid compatible with the particular individual casting component as already described in the German patent document 34 20 222 C2. However such a drive liquid compatible with the individual casting component may evince excessive viscosity for the regulators of the drive fluid. In this respect the invention provides that at least one plunger-cylinder system comprise a drive plunger for the individual component or casting material loaded by pressurized fluid, and an output plunger driven by the drive plunger by means of an intermediate fluid. The geometric spacing between the drive fluid and the individual component always precludes contact between the drive liquid and the individual component and accordingly the parts of the drive system are not contaminated by the individual components. Preferably the at least one plunger-cylinder system is driven hydraulically.
In the invention the output plunger may comprise a plunger rod passing through the drive plunger and through the cylinder head, or the drive plunger may comprise a rod passing through the cylinder head to ascertain the quantity of stored component in the particular plunger-cylinder system.
In a further embodiment mode of the invention, the plungers of the at least one plunger-cylinder system are linked rigidly together or in a variably preselected coupling ratio. If the plungers are rigidly linked, fixed composition of casting materials can be observed. Illustratively such a rigid coupling can be implemented by a plunger-cylinder system with stepped plungers and two cylinder chambers.
Another embodiment mode consists in mounting at least two separate plunger-cylinder systems with plungers rigidly joined, for instance by a yoke linking the plungers directly or else their rods. As regards a variable and preselected coupling on the other hand, operation may be carried out with casting materials of different compositions without the need to reconvert the plunger-cylinder systems or their drive. Furthermore the drive for the plungers of the plunger-cylinder systems also may be designed for a variable drive ratio of the plunger elements or for a variable mixing ratio of the individual components. As a result it will be feasible to vary for instance the quality of individual parts in order that one part of a subsequent molded article be of greater hardness while another part shall be more flexible. Illustratively the amount of flexibilizer may be varied while the mold is being filled, for instance by means of a third pump with associated storage vessel.
The coupling between the plunger elements of the at least one plunger-cylinder system can be implemented for instance in mechanical, electrical, electronic manner and/or by a pressurized fluid.
The invention provides moreover that the drive of the plungers is designed in such manner that the gelling pressure on the particular mold be kept constant during the gelling of the casting resin. As a result the at least one plunger-cylinder system shall fulfill two functions, namely metering which otherwise would be carried out by metering pumps and buffering to maintain the gelling pressure on the casting mold, any material dwindling occurring during gelling being compensated by the plunger-cylinder system(s).
The mixing chamber may be a static or a dynamic mixer.
The invention also allows designing the equipment to fill several casting molds. In one embodiment mode a buffer preceded by a shutoff device such as a check or shutoff valve is mounted in the feed conduit leading from the mixing chamber to the individual casting molds.
In an alternative embodiment mode of the invention regarding in particular casting materials of short pot lives, a separate mixing chamber, preferably a static mixer with subsequent buffer shall be associated with each casting mold and shutoff devices such as check or shutoff valves are mounted in the feed conduits for the individual components. Because the individual components are moved to the immediate vicinity of the casting mold, the reactive mixture in the particular feed conduit will be minimized. The buffer plunger can be loaded by a pressurized medium, but also by spring means and it may also be displaced mechanically.
Further objects, advantages and features and applications of the present invention are discussed in the description below and in relation to the drawings. All features, whether described and/or shown graphically, are objects of the present invention whether considered per se or in arbitrary combinations, regardless of their summarization in the claims or the claims' inter-relations.